Opposition MSPs have joined forces to criticise evidence given by civil servants to a Holyrood committee on plans to scrap the graduate endowment.
The bill would end the payment paid by Scots graduates
Labour, Tory and Lib Dem members of the Education, Lifelong Learning and Culture Committee claimed they received flawed information on the proposals.
They accused officials behind the bill of failing to ask key questions.
Education Secretary Fiona Hyslop said she was "extremely disappointed" at the actions of the committee members.
But the opposition MSPs said the officials failed to ask the Students Award Agency for Scotland (SAAS) questions on the number of students affected.
During the meeting, official Alex Young apologised to committee members for incorrectly saying that alternatives to the proposed scheme had been studied.
And he was told by the committee's convener, Labour's Karen Whitefield, that it was not possible to change documents outlining the bill after offering to do so.
North-east Labour MSP Richard Baker said: "The bill team failed to justify assertions made in the policy memorandum that the endowment has deterred students with any hard evidence at all.
"This has to be one of the poorest cases made for legislation to this parliament, and how can we have confidence in the robustness of the government's position on the endowment if they have so clearly and abjectly failed to research properly their own arguments for its abolition?"
Lib Dem education spokesman Jeremy Purvis described the evidence as "weak, contradictory and wholly unsatisfactory".
"I cannot recall an occasion where my Conservative and Labour colleagues have joined me in raising such serious procedural and evidential concerns," he added.
Tory schools spokeswoman Liz Smith said "it would be fair to conclude that the members of the committee have been misled".
Ms Hyslop said she was "extremely disappointed" that committee members had decided to criticise the officials.
And she accused opposition parties of playing politics with a policy that has "overwhelming support" throughout Scotland.
The bill aims to end the £2,289 charge, paid by Scots who graduate in this country.
Abolishing the payment was a key SNP election pledge, along with scrapping student debt repayments.
The endowment was introduced in 2001 as part of a shake-up which ended up-front tuition fees for Scottish students at Scottish universities.